Display Device Potential Maintenance Circuit for Pixel Stability
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Solution Overview
Problem
Electrophoretic display devices experience a reduction in display quality due to potential variations caused by feedthrough or leakage of holding capacitors when the pixel transistor is turned off, leading to unstable image retention.
Innovation Solution
A display device with a potential maintenance circuit that statically maintains one of three potential values (positive-polarity, ground, or negative-polarity) charged during the write period, using a configuration of transistors and capacitors to reduce potential variations and stabilize the pixel electrode potential during the hold period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the pixel transistor is turned off to hold the potential during the hold period, then power consumption is reduced and image retention is achieved, but potential variation occurs due to feedthrough or leakage of the holding capacitor, leading to reduction in display quality
Solution Approach 1:
A potential maintenance circuit is introduced as an intermediary component between the holding capacitor and ground. This circuit includes a maintenance transistor that selectively connects the holding capacitor to ground based on the potential value, thereby maintaining stable pixel electrode potential without requiring continuous transistor operation, thus reducing power consumption while preventing display quality degradation
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the connection state of the holding capacitor to ground based on the charged potential value. The potential maintenance circuit changes the electrical parameter (connection to ground) according to the potential state, which stabilizes the potential during the hold period and prevents feedthrough and leakage effects that would otherwise degrade display quality
2Duration of action of stationary object
If the pixel transistor is turned off to hold the potential, then the holding capacitor maintains the charge, but feedthrough or leakage occurs causing potential variation and unstable image retention
Solution Approach 1:
The potential maintenance circuit serves as a mediator that stabilizes the holding capacitor's potential during the hold period. By selectively connecting the holding capacitor to ground based on the charged potential value, the circuit prevents potential drift caused by feedthrough and leakage, thereby maintaining both long-term image retention and potential stability
Solution Approach 2:
The potential maintenance circuit implements a feedback mechanism where the maintenance transistor is controlled based on the potential value charged in the holding capacitor. This feedback control adjusts the connection to ground to maintain stable potential, preventing the instability that would otherwise occur during image retention
Data Source
AI summary
A display device has a write period of charging a holding capacitor included in each of pixels arranged in a first direction and a second direction different from the first direction in a display region, and has a hold period of holding capacitance of the holding capacitor charged during the write period. The display device comprises a potential maintenance circuit configured to maintain, during the hold period, one of three potential values of a positive-polarity potential, a ground (GND) potential, and a negative-polarity potential having charged the holding capacitor during the write period.